Spark gap devices

ABSTRACT

Electrical devices and methods and apparatus for making the same, involving the support of conductive portions in an insulating member. Spark gap devices are constructed by moving heated rigid pressure members together to press kinked U-shaped wires into a strip of insulating material which is preferably a glass fiber mat preimpregnated with a semicured polyester. A second strip may be used with the wires being sandwiched between the strips which are pressed together by the pressure members to fuse them. The bight portions of the U-shaped wires are severed to provide spark gaps, preferably by use of severing means associated with the pressure members. By making a plurality of spark gap devices in strip form, grooves for automatic separation may be formed by providing projections on at least one of the pressure members.

United States Patent [72] Inventors Sylvester R. Taterzynski;

George Dand Raeburn, both of Milwaukee, Wis. [21] Appl. No. 728,497 [22] Filed Mlyl3,1968 [45] Patented June 22, 1971 [73] Assignee Globe-Union inc.

1 Milwaukee, Wis.

[54] SPARK GAP DEVICES 10 Claims, 12 Drawing Figs.

[52] U.S.Cl 315/35, 174/144, 174/177,3l3/325, 315/36, 315/71, 317/69 [51] lnt.Cl. 1101! 1/16, H01t 5/00 [50] Field ofSeareh 315/32, 35, 36; 317/61, 67-69, 256; 339/17; 313/267, 283, 325, 358; 29/2512, 25.41, 624, 625; 174/140, 144, 176,177, 181, 120, 68.5, 52.6; 156/159, 228, 268. 309

[56] References Cited UNITED STATES PATENTS 3,322,995 5/1967 Hansen etal. 315/36 X Primary Examiner-Roy Lake Assistant Examiner-E. R, LaRoche Attorney-Pendleton, Neuman, Williams and Anderson ABSTRACT: Electrical devices and methods and apparatus for making the same, involving the support of conductive portions in an insulating member. Spark gap devices are constructed by moving heated rigid pressure members together to press kinked U-shaped wires into a strip of insulating material which is preferably a glass fiber mat preimpregnated with a semicured polyester. A second strip may be used with the wires being sandwiched between the strips which are pressed together by the pressure members to fuse them. The bight portions of the U-shaped wires are severed to provide spark gaps, preferably by use of severing means associated with the pressure members. By making a plurality of spark gap devices in strip form, grooves for automatic separation may be formed by providing projections on at least one of the pressure members.

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SPARK GAP DEVICES This invention relates to electrical devices and methods and apparatus for making the same, involving the supportof conductive portions in an insulating member. Although having other applications, the invention is particularly advantageous in the formation of tough and durable spark gap devices in a comparatively simple and straightforward manner, with minimum expense.

In the prior art,.the manufacture of spark gap and similar electrical devices has involved complex and costly procedures such as, for example, the complex handling of liquid casting resins and costly preforms, or the repeated dipping of wire forms in a liquid plastic material. The devices have been easily broken and subject to failure.

This invention was evolved with the general object of overcoming the disadvantages of prior art devices, methods and apparatus and of providing tough and durable devices and simplified methods and apparatus for manufacturing thereof at minimum cost.

In accordance with this invention, conductive part portions are placed against a surface of a strip of insulating material which includes a plastic material, the conductive part portions and the strip being disposed between a pair of rigid pressure members which are moved together to press the conductive part portions into the strip. Withjthis simple procedure, an insulating member is formed having the conductive part por-' tions locked in spaced relation therein.

In accordance with a specific feature of the invention, a second strip of insulating material is provided with the conductive part portions being sandwiched between the two strips and with sufficient pressure being applied'to bond the facing surfaces of the strips together.

Preferably, the pressure plates are heated to effect softening of the plastic material and to facilitate fusing of the strips together, when two strips are used.

According to another specific feature of the invention, the strips include a fibrous material, preferably a glass fiber mat, impregnated with a plastic material which is preferably a semicured polyester material. With these features, a support member is provided which is verytough and durable while being easily made.

Important features relate to the formation of a spark gap device, wherein wire which preferably has a U-shaped configuration is cut at a bight portion thereof after assembly to provide an accurately formed spark gap. In one preferred arrangement, portions of the legs of a U-shaped wire spaced from the bight portion thereof are pressed into the strips during assembly to provide a gap portion free of insulation. In another aspect of the invention, the bight portion is pressed into the insulating strip and a slot is cut through the insulating member and the bight portion to form the spark gap.

Another feature relates to the use of kinks or discontinuities in the legs of the wire to prevent twisting.

A further feature relates to the provision of wire cutting means, preferably associated with the pressure members to cut the wires while they are supported between the pressure members.

Still another feature is the inclusion of resistance wire with a partial conductive coating to provide a series impedance.

Additional features of the invention relate to the formation of a number of spark gap devices or other electrical devices at a time, the insulating member being separated into parts after formation. Preferably, one or both of the pressure members may be formed with projections operative to form grooves in the insulating member to form index marks for the cutting of the member, or to weaken the member to permit orderly breaking thereof.

This invention contemplates other objects, features and advantages which will become more fully apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate preferred embodiments and in which:

FIG. 1 is atop plan view of a spark gap device constructed in accordance with the principles of this invention;

FIG. 2 is an elevational sectional view taken substantially along line lI-II of FIG. 1;

FIG. 3 is a view illustrating a step in a method of making the device of FIGS. I and 2, in which U-shaped elements are supported and placed against a strip of insulating material;

FIG. 4 is a view illustrating another step in a method of making the device of FIGS. I and 2, in which a second strip of insulating material is placed in position;

FIG. 5 is a top plan view of apparatus in which the assembly of FIG. 4 may be placed;

FIG. 6 is ,a sectional view taken substantially along line VI-VI of FIG. 5;

FIG. 7 is a sectional view taken substantially along line VII-VII of FIG. 5;

FIG. 8 is a sectional view taken substantially along line VIII-VIII of FIG. 6;

FIG. 9 is a view similar to FIG. 4 illustrating a step in making a strip of spark gap devices of modified form;

FIG. 10 is a top plan view of a strip of spark gap devices of modified form, made by a method including the step illustrated in FIG. 9 and including effective series resistance;

FIG. 11 is a sectional view taken substantially along line XI-XI of FIG. 10; and

FIG. 12 is a schematic diagram of the embodiment of the invention illustrated in FIG. 11.

Referring to FIGS. I and 2, reference numeral 10 generally designates a spark gap device constructed in accordance with the principles of this invention. The device 10 comprises a pair of L-shaped wires lland 12 including a pair of legs 13 and 14 having terminal ends 15 and 16 spaced apart to define a spark gap, and including legs l7 and 18 disposed in generally parallel relation. Portions of the legs 17 and 18 adjacent the legs 13 and 14 are supported in a member 20 of insulating material and are preferably formed with kinks 21 and 22 to prevent twisting. The device 10 is made with a method and apparatus of the invention as hereinafter described and the member 20 preferably includes at least one glass fiber mat impregnated with a polyester and cured to be substantially rigid, thereby providing a construction which is very tough and durable.

FIG. 3 illustrates'a step of a method of the invention by which a plurality of spark gap devices such as the device 10 may be made in strip form. The construction of a strip of six devices is illustrated, but it will be understood that any desired number may be made. In particular, six U-shaped wires 23- 28 are placed on a card 30 and are held in properly spaced relation by means of a strip of adhesive tape 31. The wires 2328 are of substantially identical form and the wire 23, for example, may include a bight portion 32 and a pair of leg portions 33 and 34 formed with kinks 35 and 36. The assembly is placed so that the portions of the leg portions 33 and 34 which include the kinks 35 and 36 are disposed against a strip 37. A second strip 38 may then be placed in alignment with and against the strip 37 in a manner such that the kink portions 35 and 36 of legs 33 and 34 are sandwiched between the strips 37 and 38, as shown in FIG. 4.

The strips 37 and 38 include a plastic material and preferably also include a fibrous material which most preferably is a glass fiber mat preimpregnated with the plastic material. The plastic material is preferably a polyester material and most preferably is a semicured polyester material. Glass fiber mats preimpregnated with a B-stage or semicured polyester are commercially available. By way of example, a Fusa-Fab" semicured polyester-treated glass cloth or tape product of the General Electric Company may be used. For example, the General Electric Fusa-Fab" product No. 76,034, having a thickness of 0.03 inches may be used, and the width may be approximately inches. As another example, a Vibrin-Mat" glass reinforced polyester produce of the Uniroyal Chemical Division of Uniroyal, Inc. may be used.

Referring to FIG. 5, reference numeral 40 generally designates apparatus constructed according to the principles of this invention and usable to make the strip of the spark gap devices. The apparatus 40 includes a pair of rigid, relatively movable, pressure members 41 and 42 which are formed with mating recesses 43 and 44 which may receive the strips 37 and 38, as shown in Fig. 4, with portions of the wires 2328 sandwiched therebetween. 1n the alternative, an assembly with a single strip, such as the assembly with the single strip 37 as shown in FIG. 3, may be disposed between the members 41 and 42 along with the wires 2328, without the strip 38.

A suitable mechanism is connected through legs 45 and 46 to the member 41 to move the member 41 toward the member 42 and to apply pressure to the strip or strips within the mating recesses 43 and 44. Preferably, electric heating elements 47 and 48 are provided within the members 41 and 42 and are connected to a voltage source 50 as diagrammatically illustrated, to maintain the members 41 and 42 at an elevated temperature. As a result of the pressure and heat, the plastic material is softened and the wires 23-28 are pressed into the material. In the case wherein the two strips 37 and 38 are used, the facing surfaces thereof are fused and bonded together. In either case, an insulating member is formed having portions of the wires locked in spaced relation therein.

During and/or after the press portion of the cycle, the plastic material may be cured, either while between the pressure members 41 and 42 or after removal therefrom, or both. By way of example and not by way of limitation, a pressure of from to 30 p.s.i. may be applied in the press portion of the cycle which may have a duration on the order of 3 minutes and the members may be at a temperature on the order of from 450 to 500 F. Then, after removal from between the members 41 and 42, the formed insulating member may be postcured in an oven for a time interval on the order of 30 minutes and at a temperature on the order of 300 F.

In accordance with a specific feature of the invention, a series of spaced projections 51 and 52 are provided in the recesses 43 and 44 in mating relation, for the purpose of providing grooves in the strip of insulating material and to facilitate separation thereof into a plurality of spark gap devices. The separation may be performed by breaking or cutting.

In accordance with a further feature of the invention, the bight portions of the wires 2328 are severed to provide spark gaps. The cutting may be performed after removal from between the pressure members 41 and 42 but, in accordance with a specific feature of the invention, it is preferably perfonned while the wires are held between the pressure members 41 and 42. lo particular, a series of cutting means are provided, one of which is shown in FIG. 7. A cutter 54 of rectangular cross section is formed with a V-shaped notch at one end arranged to engage the bight portion 32 of the wire 23 and is arranged to move into an opening 56 of rectangular cross section in a mating member 57 which may be formed with a V- shaped end 58, so that the short section of the wire is sheared away, to provide the spark gap. The member 54 is supported for slidable movement in a sleeve 59 which is held in an opening in the member 42 by means of a screw fitting 60. The member 57 is similarly held in position by means of a screw fitting 61 and the devices may be removed for sharpening or for substituting of a different size of cutter. To operate the cutter member 54 and the corresponding cutting members of the other cutting means, they are locked to a bar 62 which is connected through links 63 and 64 to a suitable operating mechanism, not shown.

It is noted that the member 41 is formed with a U-shaped recess 65 for receiving and guiding the bight portion 32 of the wire and is also provided with recesses 66 and 67 for receiving and guiding the leg portions 33 and 34 of the wire 23, mating recesses being preferably provided in the member 42. Preferably, the dimensions of the recesses in the members 41 and 42 are such in relation to the dimensions of the strips as to cause the plastic material to flow into the ends of the recess 65 so as to be quite close to the bight portion so as to provide maximum support.

FIG. 9 illustrates a step in a method of forming a modified form of spark gap device. A plurality of U-shaped wires 69, similar to the wires 23-28 but without the kinked portions, are mounted on a card 75 and held in place by a strip of adhesive tape 76. The bight portions of the wires 69 are then either engaged with a single strip or sandwiched between a pair of strips 77, the strips 77 and the portions of the wires 69 therebetween, being then disposed between the pressure members 41 and 42, or a similar pair of pressure members not having the cutting means or'the U-shaped recesses 65. After pressing, heating and curing, a strip 78 is formed as illustrated in FIGS. 10 and 11 and slots 79 may be cut therein to form the spark gaps, the slots 79 having side walls aligned with the adjacent ends of the L-shaped wires formed by cutting the bight portions of the U-shaped wires.

The embodiment of FIGS. 10 and 11 incorporates an additional important feature which may improve overall reliability. The wires 69 are formed of a highly resistive metal alloy whereby high impedanccs are effectively disposed in series with the spark gap. This insures extinguishment of the arc following a momentary surge of high voltage.

Any desired portions, and especially the terminal portions 80 are coated with a much more conductive material such as a tin-lead alloy in the nature of conventional solder. Thus, the terminals are of low impedance and are readily wetted with solder to facilitate wiring to other components or to a circuit board. It is preferred that the terminal portion 80 extend into the body 78 to be certain that solderable portions exist immediately adjacent thereto, an important desideratum in circuit board wiring.

The equivalent circuit diagram of the device of FlGS. 10 and 11 is shown in FIG. 12, including the two series resistors 81 and 82.

It will be understood that modifications and variations may be effected without departing from the spirit and scope of the novel concepts of this invention.

We claim as our invention:

1. in an electrical device, an elongated strip of insulating material, and a plurality of spaced conductive wires having portions disposed transversely on a surface of said strip, said wires being fixed in spaced relationship along the length of said strip and arranged in pairs with the portions of the wires at one end of each said pair projecting toward each other in relative close proximity to define a spark gap.

2. In an electrical device as defined in claim 1, a second strip of insulating material having a surface bonded to said surface of the first strip to form an integral insulating member having said pair of conductive wires locked in transversely disposed, spaced relation therein.

3. ln a device as defined in claim 1, the portions of said wires engaged with said strip being kinked.

4. In a device as defined in claim 1, each of said pairs of conductive wires being generally L-shaped with the portions thereof at said one end being short and disposed in relatively close proximity to define a spark gap and having long terminal ends disposed for connection with an electric circuit.

5. An electrical device as claimed in claim 1, said strip of insulating material including a plastic material.

6. In a device as defined in claim 5, said strip including a glass fiber mat impregnated with polyester material cured by heating into a solid rigid mass.

7. An electrical spark gap device comprising a pair of shaped, elongate, flexible conductors, a first insulating deformable sheet, and a second insulating deformable sheet, said first and second sheets being secured together in substantially aligned, overlying relationship, portions of said conductors being entrapped therebetween, said conductors having relatively long terminal ends extending therefrom in spaced relationship, and said conductors having relatively short ends extending from between said sheets and being disposed in closely spaced, spark gap forming relationship.

8. The electrical spark gap device of claim 7 wherein said conductors are wires.

10. The electrical spark gap device of claim 9 wherein portions of said resistive conductors are coated with a hi ductivity material.

gh con- 

1. In an electrical device, an elongated strip of insulating material, and a plurality of spaced conductive wires having portions disposed transversely on a surface of said strip, said wires being fixed in spaced relationship along the length of said strip and arranged in pairs with the portions of the wires at one end of each said pair projecting toward each other in relative close proximity to define a spark gap.
 2. In an electrical device as defined in claim 1, a second strip of insulating material having a surface bonded to said surface of the first strip to form an integral insulating member having said pair of conductive wires locked in transversely disposed, spaced relation therein.
 3. In a device as defined in claim 1, the portions of said wires engaged with said strip being kinked.
 4. In a device as defined in claim 1, each of said pairs of conductive wires being generally L-shaped with the portions thereof at said one end being short and disposed in relatively close proximity to define a spark gap and having long terminal ends disposed for connection with an electric circuit.
 5. An electrical device as claimed in claim 1, said strip of insulating material including a plastic material.
 6. In a device as defined in claim 5, said strip including a glass fiber mat impregnated with polyester material cured by heating into a solid rigid mass.
 7. An electrical spark gap device comprising a pair of shaped, elongate, flexible conductors, a first insulating deformable sheet, and a second insulating deformable sheet, said first and second sheets being secured together in substantially aligned, overlying relationship, portions of said conductors being entrapped therebetween, said conductors having relatively long terminal ends extending therefrom in spaced relationship, and said conductors having relatively short ends extending from between said sheets and being disposed in closely spaced, spark gap forming relationship.
 8. The electrical spark gap device of claim 7 wherein said conductors are wires.
 9. The electrical spark gap device of claim 7 wherein said flexible conductors have substantial resistivity and thus form series resistances with said gap to assist in extinguishing an arc thereacross.
 10. The electrical spark gap device of claim 9 wherein portions of said resistive conductors are coated with a high conductivity material. 